Novaspider, one of a kind

NovaSpider is a scientific tool to fabricate multiphase nanocomposites with nanofibers combining electrospinnig, melt electrowriting and other techniques, applying a patented technology. Therefore, it allows to create pre-designed structures of three different types: ultrathin oriented fibers, random nanofibers and solid objects. For this purpose, three techniques are applied: electrospinning, melt-electrospinnig and fused deposition modeling (FDM). Other additive manufacturing technologies will be soon available.

Our advanced equipment applies the most advanced Industry 4.0 technologies to integrate several additive manufacturing techniques in a modular and simple manner. In short, flow is precisely driven by pressure or mechanically in the case of the innovative pellet extruder providing great flexibility to work a huge range of materials.

The tool was developed by a multidisciplinary team of scientists and engineers at the vanguard nanoscience research center CIC nanoGUNE. In addition, Nadetech, an expert producer of scientific equipment and industrial scale, contributes its experience.

melt electrowriting nanofibers electrospinning

Multiple advanced technologies in a single tool

melt electrowriting nanofibers electrospinning
melt electrowriting nanofibers electrospinning

Fused deposition modeling (FDM)

Fused deposition modeling (FDM) is a widely spread additive manufacturing technique to create 3D parts with thermoplastics. To sum up, this method consists on a layer-to-layer deposition of molten material that solidifies when it cools creating the desired object. In addition, It can be performed with commercial and with custom made materials.

melt electrowriting nanofibers electrospinning
melt electrowriting nanofibers electrospinning

Melt electrospinning

Melt electrospinning is a processing technique to produce fibrous structures from polymer melts. In this particular case of electrospinning, the collection of the fiber can be very focused. Therefore, combined with moving collectors, melt electrospinning writing is a way to perform 3D printing with ultrathin fibers. Moreover, polymer melts eliminates the need for volatile solvents.

melt electrowriting nanofibers electrospinning
melt electrowriting nanofibers electrospinning

Solution electrospinning

Electrospinning is a fiber production method which uses electric force to draw charged threads from polymer solutions with diameters in the order of some hundred nanometers. In short, solution electrospinnig needs the material dissolved in an appropriate solvent forming a fluid which viscosity, surface tension and conductivity must be within certain ranges.

Electrospinning

Electrospinning is a fiber production method which uses electric force to draw charged threads of polymer solutions or polymer melts up to fiber diameters in the order of some hundred nanometers. Particularly, the process shares characteristics of both electrospraying and conventional solution dry spinning of fibers. The process does not require the use of coagulation chemistry or high temperatures to produce solid threads from solution. As a result, the process is particularly suited to the production of fibers using large and complex molecules. Particularly, when we use molten precursors; this method ensures that no solvent can be carried over into the final product. [1]

Melt Electrowriting (MEW)

Electrostatic spinning (electrospinning) is a manufacturing process that draws fibers using electrical instabilities and is researched extensively to make filters, textiles and tissue engineering scaffolds. The vast majority of researchers use solution electrospinning, while only a fraction investigate melts. In general, electrospinning is not been considered an additive manufacturing technique, although near-field electrospinning is well recognized in the electrospinning community. There is, however, an underlying electrohydrodynamic (EHD) phenomenon for near-field electrospinning that is not well-appreciated.

Melt electrostatic writing (melt electrowriting), uses translating collectors or heads to place defined microfibers in a way that opens up new possibilities for many applications. Melt Electrowriting (MEW) is solvent-free, and GMP-manufactured polymers can be used as received. As an additive manufacturing process, it allows such design principles to manufacture new, orderly microstructures. [2]

Structures obtained :

The types of fibers and nanofibers obtained using electrospinning and melt electrowriting depend on the material used and its parameters such us viscosity, surface tension and conductivity. Process parameters such as distance, voltage, temperature and chamber atmosphere, specialy in the case of solutions, also affect the results.

nanofibers electrospinning
Nylon nanofibers from solution electrospinning
Solution electrospinning
  • 10 – 600 nm diameter
  • Polymers and other materials
  • Easily functionalized
Melt electrospinning
  • 800 nm – 100 µm diameter
  • Mainly Polymers
  • Controlled deposition possible
melt electrowriting
PCL fibers from melt electrospinning. Daltster at English Wikipedia / CC BY-SA
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Aligned fibers with a rotating collector

Using a rotating collector (e.g., a mandrel, a wire drum, a wheel, a cone, or a frame) in electrospinning setup as shown in the video, is the earliest, most straightforward, and simplest way to fabricate aligned fibers. Certainly, fiber alignment increased with increasing the drum speed (surface velocity) up to a critical level (12.9 m/s). Likewise, the best orientation of the ES fibers in the mat occurs when the linear velocity of the rotating cylinder surface matches that of evaporating jet depositions. Therefore, it is the high velocities and/or mechanical stretching forces that impart the ejected ES fibers taken up on the rotating cylinder surface tightly in a circumferential manner, which results in the fiber alignment. [3]

Materials

The electrospinning techniques require a fluid material with a relatively high viscosity and long molecular chains, polymers are the most suitable materials to produce using nanofibers using melt electrowriting and electrospinning. It is also possible to electrospin short molecules and monomers with sufficient intermolecular forces. Moreover, with a post-treatment, nanofibers can also be obtained from other materials such as proteins, metal oxides, carbon, metals and glasses.

Polymers

Polymer is the most common material class for electrospinning. A broad range of polymers have been electrospun which covers industrial polymers, biodegradable polymers, speciality polymers and natural polymers. Generally, these polymers should have a high molecular weight and can be dissolved in a solvent. For commercially important polymers such as polyethylene and polypropylene which dissolves in few solvents, melt electrospinning provides an alternative option. Other polymers such as polyaniline, which has low molecular weight, generally requires a second electrospinnable sacrificial polymer to be blended with it for electrospinning.

Carbon: Since most polymers are made from a carbon backbone, carbon nanofibers can be made with post electrospinning carbonization process.

Metal oxide: Many metal oxides have important industrial applications due to their catalytic properties and photoactivity. For example, the precussor to produce titanium dioxide, is often titanium isopropoxide. Finaly, a post spinning sintering process converts then the precursor nanofibers into the metal oxide nanofibers.

Metal: Currently, electrospinning is unable to produce metal nanowires directly but it can be part of a process to produce them. In short, as we use electrospun precursors and sintering to fabricate metal oxide nanofibers, the metal oxide can be reduced to form metal nanofibers. [4]

Play Video

Melt electrospinnig a variety of polymers

Molecular Weight

The molecular weight is important as to whether the polymer can be melt electrospun. For linear homogeneous polymers, a low molecular weight (below 30,000 g/mol) can result in broken and poor quality fibers. For high molecular weights (above 100,000 g/mol), the polymer can be very difficult to flow through the spinneret. Many melt electrospun fibers reported use molecular weights between 40,000 and 80,000 g/mol or are blends of low and high molecular weight polymers. [5]

Composite

Polymer matrix nanofiber composite can be routinely produced using Electrospinning with electrospinnable polymers usually produce. Blending with mixed fillers is the most common method of producing the nanofiber composite. Carbon nanotubes, clays, inorganic nanoparticles and many others have been routinely electrospun in a polymer carrier. Most reports of composite showed good distribution of the filler material below a threshold although surfactant may also be added into the solution to facilitate filler distribution.

Inorganic composite nanofibers may also be produced with electrospinning and melt electrowriting as the preliminary process. They are commonly prepared by electrospinning of its precursor material followed by sintering process to remove the organic component. These fibers may be prepared by electrospinning a mixture of precursors and sintering. [4]

Images of a wide variety of samples fabricated with NovaSpider
References

[1] Wikipedia, Electrospinning

[2] DaltonLab. 3D Printing of Tissue Engineering Scaffolds

[3] H. Yuan, Q. Zhou, and Y. Zhang, “Improving fiber alignment during electrospinning,” in Electrospun Nanofibers, 2017.

[4] Electrospintech

[5] Wikipedia, Melt Electrospinnig